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M1: Steep mountain ridges are one of my favourite places
to go rock climbing.
And we have glacial processes to thank
for the steep ridges that we find between valleys
in high mountain ranges.
We call these ridges arêtes.
During the last ice age, this ridge in the Brecon Beacons
had glaciers on both sides of it.
Down here in this valley and over on the other side.
(bright pop music)
Those glaciers carved steep-sided U-shaped valleys.
And those steep sides drop away on either side of the ridge.
In areas more recently covered by glaciers,
knife-edged arêtes have almost vertical sides,
like the face of the Miroir d'Argentine
in the Swiss Alps.
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Here in the Brecon Beacons,
the last glaciers melted about 12,000 years ago,
and since then, weathering and hillslope creep
have been smoothing the top of this arête,
creating this lovely dragon's back ridge.
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